MODELS STUCK IN GEAR

Hello, I am having a problem with the manual transmission of my car, its the following: everytime I am driving on second gear suddenly the gear stuck, but only if I drive on it for a long time or when I go up a slope. If I drive on second gear for a short time I always can disengage it. I would like to ask another question too: Is the blocking ring locked in the sleeve of the synchronizer gear? Does the blocking ring is pulled with the sleeve in the disengagement process? Whats the real function of the inserts( keys) and their srpings? Thanks you a lot